Hi!

I have a 315 cpu and (in order 3X DI32X24Vdc ; 2X DO 16X REL AC120/230V ; 2 AI8XRTD )

I nead to measure pt1000 (4 wire) on the ai card, but when i test it i got zero for the input value.

I deactivate te unused chanels, make group diagnostik for wire break (its working). in the first group i made the configuration for the pt 1000... I try almost everything but when I monitoring the input its always 0.

In tia the hardware config is ok for every card.

Any idea?

Thanks for the ansewers and sorry for my english...

Hello,

What address are you reading? And what addresses are reserved in HW-configuration?

Best regards,

Wizard

The input adresses are directly made by tia portal when I configured the card

ch0 IW356

ch1 IW358

ch2 IW360

I only taged these...and try to monitor it in force table. After that I try to put the inputs to a database. but nothing. Only Input reading is 0 for every chanel.

...

Hi, Vincent!

Try this:

Devices&Networks -> Device View -> select your PLC;

Properties of CPU -> General tab -> Cycle:

Size of the process image input: Here put in a number, greater than your input address of analogue input; (for example, set it to 400) it should work then.

The same goes for Size of the process image output.... .

Other possibility is to set your HW addresses for analogue inputs below the value, set in parameter "Size of the process image inputs"... .

I believe, I have seen on forum another solution for this, something with ":" in syntaks for reading such inputs, but I do not remember at the moment the exact syntaks....

Maybe somebody knows that (and of course, a background?)

Have fun!

uel123. 

uel123

Hi, Vincent!

Try this:

Devices&Networks -> Device View -> select your PLC;

Properties of CPU -> General tab -> Cycle:

Size of the process image input: Here put in a number, greater than your input address of analogue input; (for example, set it to 400) it should work then.

The same goes for Size of the process image output.... .

Other possibility is to set your HW addresses for analogue inputs below the value, set in parameter "Size of the process image inputs"... .

I believe, I have seen on forum another solution for this, something with ":" in syntaks for reading such inputs, but I do not remember at the moment the exact syntaks....

Maybe somebody knows that (and of course, a background?)

Have fun!

uel123. 

hi,

 the other solution is to use the peripherial access to the input/output-variabel with e.g. %IW256:P

here is the background:

The process-image of inputs is updated before OB1-cycle from periphery and the process-image of outputs is written after OB1-cycle. The variables from the process image are normally used for digital inputs/outputs. Inbetween the OB1-cycle you can work with  e.g. %I2.2, that is a access to the input image, not direct to the input. The peripherial access is a direct access to the input/output. this is normally used for accessing analogue values. So when you project an analogue I/O, Step7 is adressing it automatically in perpherial range.

hope this helps,  

regards,

Hi, Mop, thank you very much for explanation!

Yes, I remember, with "old" step 7, usual way to read Analogue input was "PIW 512" (it meant peripheral input....). After going to TIA with "old" type CPU-s (S7300 or S7400), i somehow misssed the new syntax for accessing peripheral inputs directly... (we, "older" programmers are a little bit lazy, when it comes to reading manuals...).

So, I will remeber now the new syntay for that....

Have fun!

uel123.